1. Field of the Invention
The present invention relates to a changing device for shaft and hub connections, including a shaft end, a hub surrounding the shaft end, and a bushing disposed in between for radially clamping the hub.
2. The Prior Art
These types of changing devices for shaft and hub connections are known, for example from xe2x80x9cTaschenbuch fxc3xcr den Maschinenbauxe2x80x9d [Handbook of Mechanical Engineering] (of DUBBEL, 18th edition, G25, illustration 33f).
When the hub is to be changed, however, the drawback is that a safety nut and a safety ring have to be completely removed so that the hub can be pulled off. This leads to costly additional work steps and prolongs the tool changing time.
An object of the present invention is to develop a changing device for shaft and hub connections of the above type, which permits quick changes of hubs with plain cylindrical bores, while all other parts of the shaft and hub connection remain mounted on the end of the shaft. Furthermore, the device ensures a safe transmission of forces and torques between the shaft and hub, and a precise repeatability of the axial position of the hub relative to the shaft. When the shaft and hub connection is released or clamped, the friction between the components moving in relation to each other is kept as low as possible. Furthermore, it is an object of the invention to permit the location of a shaft bearing close to the face of the hub which is opposite to the side of the shaft end. It is necessary to locate the shaft bearing next to the hub in order to transmit the radial forces generated by the operation of the machine directly from the hub into the shaft and to the shaft bearing, thereby minimizing any elastic deflection of the shaft which might reduce the precision of the rolling process in the machine.
According to the invention, there is provided a conical bushing between the end of the shaft and the hub, and means for safely retaining the bushing on the end of the shaft which at the same time provide an axial displacement of the bushing relative the end of the shaft in both directions. The outside diameter of the means for safely retaining the bushing is at least slightly smaller than the inside diameter of the hub, and these means are located on the side of the hub which points towards the end of the shaft. Axial displacement in both directions is initiated hydraulically so that the shaft and hub connection can be safely clamped and released and the hub can be quickly changed. Furthermore, the axial movement of the bushing during the clamping action presses the hub axially against a shoulder on the shaft which leads to an enhanced adjustment of the hub with regard to its axial position and its face runout.
In another object of the invention for safely retaining the clamping bushing and simultaneously initiating an axial displacement, there is provided a clamping pin rigidly mounted on the end of the shaft, and a nut screwed on to the clamping pin. In this way, the inside step of the bushing engages an intermediate space formed by an outside step of the clamping pin and the nut, to preserve the axial play of the bushing. Thus, a very simple and favorably priced engineering solution is provided with a flawless function.
It is useful if the nut and the outer step are each provided with circular grooves on their sides facing the inside step. Each nut and step displaceably receives a sealing ring and a pressure ring, so that the clamping pin and the nut each have means for building up pressure in the grooves. In this way, an axial displacement of the bushing can be easily and reliably initiated by the nut and the circular step, and the pressure rings inserted in their grooves.
In another useful embodiment of the invention, a fitted ring is provided between the end of the shaft and the clamping pin. The clamping pin can be fitted into the end of the shaft as required, and the required axial path of displacement of the bushing leading to radial clamping of the hub part can be preadjusted.
According to the invention, there is also provided means for safely retaining the bushing so that it cannot be lost, while at the same time biaxially displacing the bushing relative to the end of the shaft. The means for safely retaining the bushing are at least slightly smaller than the inside diameter of the hub part with respect to their spatial width perpendicular to the end of the shaft. The means for safely retaining the bushing are designed in the form of a part permanently mounted on the end of the shaft, and a receiving part movably connected with the part for a double-acting axial support. A means for transmitting an axial component of motion of the receiving part to the axial support is provided, and simultaneously transmitted to the bushing. This assures quick change of the hub part, and a safe clamping of the shaft and hub connection as well. Furthermore, there are comparatively low frictional forces as the changing device is being actuated, and the bushing is only moved axially, which provides a flawless adjustment of the part.
In a further advantageous object of the invention, the receiving part is rotatably connected via an inside thread with the outside thread of the part permanently mounted on the end of the shaft. In this way, there is a biaxial displacement of the bushing in a very easy and reliable way, and very precise paths of displacement can be adjusted.
The invention also provides that the double-acting support on the receiving part is axially fixed, and the biaxial displacement of the receiving part is transmitted to the bushing or an additional part fastened on the bushing. It is very advantageous if the double-acting support is fixed via a shaft nut against a step of the receiving part. This leads to a simple and safe axial securing of the support, and reliable further transmission of an axial component of motion of the receiving part.
In a highly useful embodiment of the invention, provision is made for a sealing ring between the double-acting axial support and the shaft nut, using radial sealing elements. This leads to increased protection of the double-acting axial support and thus a longer useful life.
If the part permanently mounted on the end of the shaft has a flange or step corresponding with a circular cavity of the end of the shaft, a reliable and space-saving connection of the part can be provided, permanently mounted on the shaft end with the end of the shaft, and axial securement of the part can be provided in an easy manner.
Additional axial guidance of the receiving part can be easily provided if the part, permanently mounted on the end of the shaft, has a cylindrical section corresponding with an inside diameter of the receiving part.
To easily actuate the alternative changing device, the receiving part can have a nut-shaped end or, alternatively, a cavity-like recess on the face side.
According to an advantageous embodiment of both alternative embodiments of the invention, the bushing is provided with a conical inside zone and the end of the shaft is conical, so that the conical inside zone corresponds with the conical end of the shaft. In this way, the outside diameter of the bushing can be designed cylindrically, which leads to a design of the hub part that is simpler, and which simplifies the adjustment of the hub part.
Advantageously, the bushing is provided with longitudinal slots, which provides good radial deformability. Moreover, the longitudinal slots are cast in an elastic sealing material in order to prevent any penetration of dust, water, dirt or the like.
The changing devices of the invention can be used very advantageously in connection with floating bearings of hub parts. However, the changing devices according to the invention are also useful in connection with double-sided bearings of the hub part. In this case, it is advantageous if the bushing has zones with a cylindrical surface having a diameter smaller than the inside diameter of the hub part. Thus, the hub part can be easily pushed over the bushing without the risk of damaging the smaller cylindrical outer surface serving as the bearing seat.